Considerable efforts have been expanded in the past to flame retard thermoplastic resin without the use of halogen. Typically, it has been necessary to heavily fill the plastic or thermoplastic material with additives until the desired degree of flame retardancy is achieved. Heavy filling offers several disadvantages due to the fact that a large proportion of additives can normally be expected to detract from the physical properties of the plastic material. Further, the additive may bring complications inherent to the additive itself, such as, for example, foaming, which must be dealt with an addition to a general lessening of physical properties.
The present invention provides flame retardant additives which not only provide improved flame retardance in the absence of organic halides, but also do not exhibit poor processability as might be expected from the prior art.
U.S. Pat. No. 4,387,176, assigned to the instant assignee, discloses a flame retardant additive for thermoplastics which contains a silicone oil, a silicone resin, and a Group IIA metal salt. This flame retardant additive is most effective with the addition of a halogen.
U.S. Pat. No. 4,115,351 discloses synthetic fibers dipped in solutions containing inorganic phosphorus and inorganic nitrogen compounds. To render the compounds more convenient for use in the dip solution, they are coated with inactivating materials including silicone, paraffin, and grease.
U.S. Pat. No. 3,936,416 discloses the use of ammonium polyphosphate and dipentaerythritol as a flame retardant in polypropylene. In addition to insufficient flame retarding effect, there is a problem of flame retardant foaming during melt processing of the polypropylene.
It is an object of the present invention to produce a non-halogen containing flame retardant additive for thermoplastic resin.
It is another object to produce a non-halogen containing flame retardant additive with improved flame retardant effect.
It is yet another object of the present invention to produce a phosphorus and nitrogen containing flame retardant for thermoplastic resins which does not foam during melt processing.